Magnetic bubbles could shield astronauts from radiation

Solar storms' dangers would lessen on long space trips

SHIELDS UP A small magnet in a laboratory deflects a jet of particles by forming a thin electric skin. The same principle could be applied to create deflector shields that protect spacecraft from solar radiation.

Deflector shields aren’t just for the starship Enterprise. One day, giant magnetic bubbles could protect spacecraft on long voyages.

By gathering charged particles floating through space, the bubbles could form a force field that flicks away radiation. If successful, the idea could offer scientists a solution to one of NASA’s stickiest problems: how to shield astronauts from harmful cosmic rays and solar eruptions.

Storms on the sun catapult charged particles into space at tremendous speeds, says plasma physicist Ruth Bamford of the Rutherford Appleton Laboratory in Didcot, England. “If you’re on a spaceship in transit to Mars,” she says, “these charged particles can smash through the hull and smash your DNA.”

There are two ways to protect astronauts: shield them or shorten their travel times, says physicist Robert Winglee of the University of Washington in Seattle. In the 1960s and 1970s, Apollo astronauts avoided danger because their short missions occurred when the sun was quiet. “The astronauts dodged the bullets,” Bamford says. But Mars is hundreds of times as far as the moon. Juicing up spacecraft propulsion systems would speed space trips but is still a long way off, Winglee says, so scientists are trying to tackle shielding.

Bamford and colleagues have an idea how to do it. They’re drawing inspiration from the moon.

Two years ago, her team proposed that magnetic bubbles protect swatches of the moon’s surface from streams of solar particles (SN: 8/11/12, p. 8). The bubbles help generate an electric field that deflects the streams.

Bamford and her team thought bubbles could protect spacecraft too. They envisioned ships fitted with onboard electromagnets to generate magnetic fields. In space, a sparse smattering of peppy particles, or plasma, loosely fills the void, like a handful of sand strewn through a vast ocean. As a ship journeyed out to Mars or some other distant destination, these particles would smack into the magnetic bubble.

“It’s like hitting a wall,” says plasma physicist Daniel Spicer of Drexel University in Philadelphia. Heavy particles such as protons lodge within the wall, while lighter electrons bounce off it, he says.

A protective electric field would form as the wall separated plasma’s positive particles from its negative ones, Bamford’s team calculated.

And releasing a cloud of particles from the spacecraft — before radiation from a solar storm arrived — could offer even more protection, the researchers suggest in a paper posted June 4 at arXiv.org.

Testing whether plasma could help a magnetic field shield a spacecraft from solar flares is tricky because mimicking the sun’s storms in the lab is nearly impossible. So Bamford’s team used a computer simulation.

According to the simulation, the electric shell formed by the duo of magnet and plasma could deflect 95 percent of the speediest solar particles, protecting the interior of the spacecraft and presumably the astronauts residing there.

“It’s a promising approach,” Spicer says, “but a lot of things could go wrong.” Winglee notes that the paper doesn’t address the magnetic field’s effects on the astronauts.

Bamford wants to gather experimental evidence to test the idea and envisions trying to protect unmanned satellites orbiting the Earth. “This could be a relatively cheap mission that we could pull together in about five years,” she says.